Meteorology: Signs in a Clear Sky

It strikes with the swift, clawed fury
of a pouncing catand jet pilots call it by that name. CAT (for clear
air turbulence) can swat a jetliner down a mile in a minute flat, paste
passengers to the ceiling, and rip the wings from light planes. Many
CAT victims go uncounted because up to now CAT has been invisible.

Clear air turbulence often occurs where two air masses, moving in
opposite directions, grind together. Unlike storm fronts, which present
a large, moist target for regular storm-tracking radars, this abrupt
change of wind direction,...